On Sunday afternoon, Lauren Ambrose strode out of Henry Higgins’s Wimpole Street house and up the aisle of the Vivian Beaumont Theater for the last time.

Since the first performance on March 15, she has played what Jesse Green of The New York Times called “a feral and then luminous” Eliza Doolittle in “My Fair Lady” nearly every day and twice on Wednesdays — through antibiotics fog and deep personal loss and rollicking high school matinees.

On Sunday, just before she went to dress for her final performance, Ms. Ambrose, who is leaving to shoot M. Night Shyamalan’s new series for Apple, spoke, with perfect diction, about saying goodbye to Eliza — and the boots she wouldn’t mind snagging on her way out. (Laura Benanti starts in the role Tuesday.) These are edited excerpts from the conversation.

What have you learned about Eliza that you didn’t know at the first preview?

How alone she is at the beginning and how much she needs everyone in the play to make her transformation. And how funny the character is. I guess I learned how to trust the writing, how to fall and let the words catch me. That has come after 200 plus performances. You get to kind of soar, which is exciting and fun and daring. The words are your net.

How can you tell if the show is really working — if it’s a good night?

I can’t. I don’t know. I usually ask [my co-star] Allan Corduner. Audiences differ. Sometimes it’s like a rock show, sometimes it’s like a library, and that means they’re listening. My husband always laughs at me. I’ll come home and say, ‘It was off, it was really off.’ And he’ll say, ‘I watched it, and it was exactly the same as always.’

What was the hardest part of the show?

I dropped out of a few performances when my dad passed away about a month ago. The show was something that my dad was so very proud of. He was at opening night, even though he was very ill. To get to come back to the show and be surrounded by this amazing group of beautiful, feeling artists as I started the process of grieving and dealing with this new phase of life was really a gift, even though obviously incredibly challenging.

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Harry Hadden-Paton as Henry Higgins, working on diction with Ms. Ambrose’s Eliza.CreditSara Krulwich/The New York Times

It had been a very intense time, an awful, weird time. I had this vocal problem for a little while, my voice was cutting out while I was singing. There were a few performances where I was having a crazy muscle tension thing. It was when I was going back and forth from New Haven, from the hospital. That was really stressful; my body wasn’t responding and performing the way I wanted to. But it was amazing how supported I was by all of the people here.

What was the most fun?

The Ascot scene is always fun. Everyone enjoys it so much.

Is there any prop or any piece of costume that you’ve been tempted to take with you?

My dresser gave me the most amazing little gift last night as we were taking apart the dressing room: Eliza in a jar — swatches of all my clothes in a Mason jar. I have a little relic of every costume.

Actually, there is a pair of LaDuca boots that were made for me that I kind of rejected, because I was supposed to wear them at the end, but they were really high, and I was like, I can’t. They’re really beautiful.

Has the role changed you?

As an artist, I definitely developed muscles that I never had before and new levels of flexibility. A show like this, it’s so huge, you have new people coming in all the time and people calling out, people leaving — [my co-star] Harry [Hadden-Paton] is off doing the “Downton Abbey” movie. It’s just constantly shifting. [Mr. Hadden-Paton rejoins the cast on Tuesday.]

What was your worst performance?

Early in previews, and I had a sinus infection, and I took an antibiotic that I had a really bad reaction to. I felt like I was going to throw up, and I was on a turntable that was literally spinning. I thought, If I can get through this, I can get through anything.

Your best?

Harry’s and my last performance, that was really a peak experience, a very holy experience. We all met up before the show and had a moment all together as a cast, and it just felt like a very unified thing that was reaching its fruition and pinnacle, the ripest moment of its truth.

Our bows were hilarious. We were just clutching each other and bowing together. We didn’t do single bows. It was this weird, spontaneous thing we did. People were probably wondering what the heck was going on there.

A version of this article appears in print on , Section C, Page 5 of the New York edition with the headline: Ever So Properly, a Fair Lady Says Farewell. Order Reprints | Today’s Paper | Subscribe